Specific collagen peptides supplementation increases collagen type I content in skeletal muscle after 12 weeks of high-load resistance training: a randomized controlled trial.

Objective: The extracellular matrix is essential for skeletal muscle function, providing structural support and facilitating force transmission from muscle fibers to tendons and the skeletal system. Collagen structures, known for their high plasticity, adapt to various stimuli, including mechanical loading during high-load resistance training. The present study aimed to assess the impact of specific collagen peptide (SCP) supplementation, combined with resistance training, on the levels of intramuscular collagen (COL) types I, III, and IV, and to assess the change in intramuscular fibroblast content. Methods: In a randomized, placebo-controlled study, 29 healthy male participants completed 12-week high-load resistance training (70-85% of 1 repetition maximum) with daily supplementation of 15g of SCP or placebo (PLA). Before and after the intervention period, muscle biopsies from the vastus lateralis muscle were obtained to quantify intramuscular collagen amount and fibroblast density. Results: SCP supplementation together with exercise led to increased (p = 0.026) collagen type I content (29.8%) compared to training with placebo (9.9%). Collagen types III and IV content increased significantly across the pooled sample (p < 0.05) with no significant group x time interaction. Fibroblast density did not change over the time course of intervention, either within or between groups. Conclusion: Endomysial collagen type I content increased in response to resistance training when supplemented with SCP compared to placebo. The observed increase in intramuscular collagen content may contribute to improved structural support of skeletal myofibers.